Information about the occupancy of a given finite area can have many uses, from safety enhancement to marketing science. Here, an “occupant” is typically a person but can also be an animal, a mobile machine, or any changeable aspect of the finite area that affects radio propagation and that it may be desirable to sense. Sensed occupancy information can vary in completeness and value: e.g., one may estimate the total number of occupants at a given time, estimate statistical aspects of occupants' movements over time, or estimate tracking the movements of occupants over time.
Occupancy has been measured by manual count (e.g., at venue entrance), computer vision systems, electric-eye counters, and other methods. In recent years, a number of systems and methods have been proposed for occupancy detection within a particular area utilizing radio frequency (RF) based technologies. Examples of such systems include video sensor monitoring systems, radio frequency identification (RFID) systems, global positioning systems (GPS), and wireless communication systems among others. However, many of these systems have several disadvantages. For example, the video sensor monitoring system requires a considerable number of dedicated sensors that are expensive and the system requires a large amount of memory for storing data. The RFID systems rely on occupants carrying an RFID tag/card that can be sensed by the RFID system to monitor the occupants. The GPS system uses orbiting satellites to communicate with the terrestrial transceiver to determine a location of the occupant in the area. However, such systems are generally less effective indoors or in other environments where satellite signals may be blocked, reducing accuracy of detecting the occupant in the area. There also have been proposals to detect occupants in an area based on effects on an RF signal received from a transmitter due to the presence of the occupant(s) in the area. These RF wireless communication systems generally detect an occupant in the area based on change in signal characteristics of a data packet transmitted over the wireless network. However, all the above methods require human effort and/or dedicated hardware (e.g. cameras, directional transmitters, etc.) that entail complexity and expense. Also, an inaccurate detection of the occupant in a region can occur by detecting an object, which does not move when multiple transmitters are transmitting the RF signals from multiple different regions of the area.